Lacing attachment for airplane cover fabric



Aug. 1, 1939. K SCHMIDT LACING ATTACHMENT FOR AIRPLANE COVER FABRICFiled March 9, 1958 2 Sheets-Sheet 1 INVENTOR BY KARL SCH/Vl/DT W/MQW;

ATTORNEY 1, 1939- K. SCHMIDT LACING ATTACHMENT FOR AIRPLANE COVER FABRIC2 Sheets-Shet 2 Filed March 9,, 1938 IINVENTOR KA RL SCH M I DT ATTORNEYPatented Aug. 1 1939 "UNITE o- STATES LACING ATTACHMENT FOR. AIRPLANECOVER. FABRIC Karl Schmidt, United States Navy Application March- 9,

4' Claims.

1938, Serial No. 194,888

(Granted under the act of March 3, 1883; as

amended April 30,

The present invention relates to airplane fabric attaching means and ithas a particular relation to the attachment of the fabric to the wingsand fuselage of an airplane by means of a 5 lacing cord.

Airplane fabric cover failures may usually besubscribed to two causes,first, to the failure of the lacing cord itself, and-second, to thetearing of the fabric as a result of a concentration of the load at thepoints of its attachment to thevving rib or other supporting framemember. The first cause may result from thestretching of the lacing cordunder load and its consequent abrasive action against the edges of thecapstrip to which the fabric covering is attached. Cord failure mayalso-result at a load value far below the full cord strength, due to thecord axis being deflected so that the component threads or strands ofthe cord are non-uniformly stressed. 20- For example, if all of thecomponent threads of the cord are equally stressed, such as would be thecase where the cord is subjected to a pull exerted in a rectilineardirection, the ultimate cord strength developed may be considered as 100percent. If now, two cords are overlapped so that each cord is bent atan angleof 90 at the point of overlap or engagement, and if each cordissubjected to equal strain, the breaking strength will be approximately45 percent of the full cord strength. If, however, the cords areoverlapped at an angle of 90 or'so that the interengaging cords are bentupon themselves to extend parallel to one another and are subjected to.qual strain, the breaking strength of each cord at the point of bendwill be approximately 35 percent of full cord strength; This reductionin the strength of a lacing cord manifests itself particularly at pointswhere the cord is tied or knotted. From this it will be apparent that 40thestrength of the cord decreases with the angle of bend and that ifmaximum strength is to be obtained the cord should be subjected, asnearly as possible, to strains exerted rectilinearly of its length.

One of the objects of the invention is the provision of a method oflacing a fabric covering to the capstrip of an airplane rib or the likein which the cord is not tied off or knotted at intervals along thelength of the capstrip, thus not only increasing the tensile strength ofthe cord but obtaining a smooth cover surface which is highly desirableto improve the aerodynamic efiiciency of the airfoil and the airplane asa whole.

Another object of the invention is the provision of a lacing attachmentfor airplane wing fabric such aswill prevent'the top and bottomcoverings of the wing in the region of the propeller slipstream fromslapping against the capstrips of the ribs, which action causesexcessive Wear and early failure in the present type of coverattachment.

With these and other objects in view, as well as other advantages thatmay be incident to the use of the improvements, the invention consistsin the parts and" combinations thereof hereinafter set forth andclaimed, and-with the understanding that the several necessary elementsconstituting the same may be varied inproportion and arrangement withoutdeparting from the nature and scope of. the invention, as defined in theappended claims.

In order to make the invention more clearly understood, there are shownin the accompanying drawings; means for carrying the invention into'practical use, without limiting the improvements in their usefulapplication to the particular construction, which, for the purpose ofexplanation, have been made the subject of illustration.

In the accompanying drawings:

Fig; 1- isa diagrammatic perspective view of a fragment of an'airplanewing in which the fabric covering is secured at intervals to the rib bya lacing attachment embodying the invention; and

Fig. 2 isa similar view of another form of cover attachment embodyingthe invention.

Referring to the drawings, and particularly to Fig; l thereof, the upperand lower fabric coverings H] and II respectively, of an airplane wingis shown as being secured to the upper and lower capst-ripsa'and b of arib member, a portion of which isinclicated at IZ; by means of' a cord'lacing 1'3; This cordext'en'ds upwardly and diagonallyalong'one'side'ofthe rib, as at I4, thence through the fabric Ill andtransversely across the rib at right angles to its longitudinal axis, asat 'I5-and' downwardly through the fabric l0. From this point the cordextends downwardly across theside of therib, as at l6; and through thefabric-H, thence beneath. the rib, as at H, thence upwardly across theopposite side of the rib, as at l8; and againthrough the fabric. ID ator adjacent to the point Where it first passed therethrough. Fromherethecordis' passed severartimes' aroundth'e' portion [5 thereof, as at I9;to form an interlock A. At this point it is important that the cord betightly drawn up, thus introducing and securing initial tension in thefinishedloop. The cord then is passeddownwardly through the fabric I'll,or at near the point where the'portion M'Was'passe'd'. The cord is nextextended downwardly and" diagonally across the sideoftherib'opposite to'the diagonal portion M of the cord, as atv 20', and through the lowerfabric coveringll, thence" beneath the rib at right-angles thereto, asat 21, thence upwardly through the lower fabric covering II and acrossthe side of the rib opposite to the portion 20, as at 22, and throughthe upper fabric covering I0, thence across the upper edge of the rib,as at 23, and downwardly through the upper fabric Ill, thence downwardlyalong the side of the rib, as at 24, and through the lower fabriccovering II at or adjacent to the point where the portion 20 previouslypassed. From here the cord is passed several times around the lowerportion 2| of the cord, as at 25, to form an interlock B, and upwardlythrough the lower fabric covering II. From here on the described lacingsteps are repeated, each loop being drawn up tightly before starting thenext one. It will be noted that the upper and lower coverings Ill and IIare thus secured by spaced loops extending at right angles to the riband that the loops are all connected by diagonally extending portions ofthe same lacing cord. Also, it will be noted, that by this method oflacing, the upper and lower coverings are held in position by alternateportions of single and double cord strength, the cords of the latterbeing twisted together and later united by the finishing dope.

In Fig. 2 there is illustrated another method of lacing cord attachmentembodying the invention -in which the lacing cord is first passeddiagonally downward through the lower fabric covering II, as at 25,thence beneath the rib, as at 21, thence upwardly through the lowerfabric H and upwardly across the far side of the rib, as at 28, thencethrough the upper fabric covering it] and across the upper surface ofthe rib, as at 29, thence downwardly through the fabric l0 and acrossthe near side of the rib, as at 30, and thence through the lower fabriccovering l I at or near the point where the diagonal portion 26 of thecord passed therethrough. From here the cord is passed several'timesaround the lower portion 21 of the cord, as at 3|, and upwardlythrough'the lower fabric II, at or near the point where the portion 2'!passed, thence upwardly across the far side of the rib parallel to theportion 28, as at 32, and through the upper fabric, at or near where theportion 28 passed. The cord is then passed several times around theupper portion 29 thereof, as at 33, and downwardly through the upperfabric I0. From here on the above described lacing steps are repeated.This form of lacing differs from that described in connection with Fig.1 in that the transverse portions of the cord which are disposed incontact with the upper and lower coverings are all of double cordstrength.

From the foregoing it will be apparent that by means of the present formof lacing a. fabric covering may be secured to a wing rib or other framestructure without the use of knots or sharp bends in the cord, thusutilizing nearly the full tensile strength of the cord. The portions ofthe cord where they are twisted together, as at A and B, greatlyincrease the resistance to slippage and elongation of the cord,especially when dope impregnated. Also, as has been hereinbefore pointedout, the elimination of the many knots, previously employed in this typeof lacing, results in a smooth wing surface of low wind drag.

The method of lacing herein described may be further modified in itsapplication by those skilled in the art without departing from thenature and scope of the invention as defined in the appended claims.

The invention described herein may be manufactured and/or used by or forthe Government of the United States of America for governmental purposeswithout the payment of any royalties thereon or therefor.

I claim:

1. An airplane wing construction comprising a rib member having upperand lower capstrips connected together; upper and lower fabric coveringssupported by said rib; and a lacing cord for securing said coverings tosaid capstrips; said lacing cord passing continuously around saidcapstrips and through said upper and lower coverings in a series ofspaced loops, the portions of said cord connecting said loops beingtwisted around certain of the transverse portions of said loops to forman elongated interlock for and between adjacent loops, whereby slippageand elongation of the cord is reduced and friction between theinterlocking portions of said cord and between said cord and saidcoverings is distributed throughout the width of said capstrip.

2. An airplane wing construction comprising a rib member having upperand lower capstrips connected together; upper and lower fabric coveringssupported by said rib; and a lacing cord for securing said coverings tosaid capstrips; said lacing cord passing continuously around saidcapstrips and through said upper and lower coverings is a series ofspaced loops, the portions of said cord connecting said loops beingtwisted around certain of the transverse portions of alternate loops toform an elongated interlock for and between adjacent loops, wherebyslippage and elongation of the cord is reduced and friction between theinterlocking portions of said cord and between said cord and saidcoverings is distributed throughout the width of said capstrip.

3. An airplane wing construction comprising a rib member having upperand lower capstrips connected together; upper and lower fabric coveringssupported by said rib; and a lacing cord for securing said coverings tosaid capstrip; said lacing cord passing continuously around saidcapstrips and through said upper and lower coverings in a series ofspaced loops, the portions of said cord connecting said loops beingtwisted around certain of the inner and outer transverse portions ofeach of said loops to form an elongated interlock for and betweenadjacent loops, whereby slippage and elongation of the cord is reducedand friction between the interlocking portions of said cord and betweensaid cord and said coverings is distributed throughout the width of saidcapstrip,

4. An airplane wing construction comprising a rib member having upperand lower capstrips connected together; upper and lower fabric coveringssupported by said rib; and a lacing cord for securing said coverings tosaid capstrip; said lacing cord passing continuously around saidcapstrips and through said upper and lower coverings in a series ofspaced loops, the portions of said cord connecting said loops extendingdiagonally across the sides of said capstrips and twisted around certainof the transverse portions of said loops to form an elongated interlockfor and between adjacent loops, whereby slippage and elongation of thecord is reduced and friction between the interlocking portions .of saidcord and between said cord and said coverings is distributed throughoutthe width of said capstrip.

KARL SCHMIDT.

